13.1 BACKGROUND

Provide the basic engineering material properties of the pavement structure that support a wide variety of performance analyses.

Provide a measure of the variation in the pavement structure and material properties.

The original materials characterization scheme was based on materials testing and parameters that existed in the late 1980s. Updates to a few tests, most notably the resilient modulus of AC materials, were made in the 1990s. Overall, the intention of the LTPP program is to focus on materials tests in common use at the initiation of the project, so that upon completion, a full suite of results will be available for the entire timespan.

The LTPP program developed materials sampling and testing protocols primarily based on in-place material samples from pavement structures, although for some tests on SPS sections or GPS overlay sections, materials were sampled during construction. These protocols are documented in SHRP-LTPP Interim Guide for Laboratory Materials Handling and Testing and SHRP-LTPP Guide for Field Materials Sampling, Testing, and Handling. In addition, materials sampling and testing guidelines were developed for each SPS experiment. A list of these guidelines is presented in appendix A.

The LTPP materials sampling and testing program began on GPS test sections accepted into the program before 1990. An initial round of sampling and testing was conducted in 1989. LTPP contractors conducted the field materials sampling and testing and laboratory testing for these sections. For SPS sections and GPS overlay sections, the respective highway agency is responsible for most materials testing. Resilient modulus and associated testing of hot-mix asphalt (HMA) materials and the coefficient of thermal expansion of PCC materials are conducted by LTPP-contracted laboratories.

13.2 MATERIALS TEST TYPES

A list of typical materials tests, test designations, and protocols are shown in table 5. The test designation is used for database table names. The tests actually conducted on a test section are dependent on the type of materials, the thickness of the material layers, and the type of pavement layer. Test requirements also vary according to the objectives of the experiment to which the section is assigned. In some cases, a layer may not have been thick enough to meet testing requirements for bound materials or sufficient quantities of materials could not be obtained in order to conduct a test.

LTPP Database Tip!

Perform an evaluation of data availability. Do not assume that all planned materials tests are available.

Table 5. Materials testing designations and protocols.

Material

Test Designation

Name

Protocol

Asphalt Concrete

AC01

Core Examination and Thickness

P01

Asphalt Concrete

AC02

Bulk Specific Gravity

P02

Asphalt Concrete

AC03

Maximum Specific Gravity

P03

Asphalt Concrete

AC04

Asphalt Content (Extracted)

P04

Asphalt Concrete

AC07(1)

Resilient Modulus, Tensile Strength, and Creep

P04

Asphalt Concrete

SP01(1)

Gyratory Compaction

(4)

Asphalt Concrete

SP02(1)

Volumetric and Gravimetric Properties of Superpave Mixes

(4)

Extracted Aggregate From Asphalt Concrete

AG01

Specific Gravity of Coarse Aggregate

P11

Extracted Aggregate From Asphalt Concrete

AG02

Specific Gravity of Fine Aggregate

P12

Extracted Aggregate From Asphalt Concrete

AG04

Gradation of Aggregate

P14

Extracted Aggregate From Asphalt Concrete

AG05(2)

Fine Aggregate Particle Shape

P14A

Asphalt Cement

AE01

Abson Recovery

P21

Asphalt Cement

AE02

Penetration at 77 ° F and 115 ° F

P22

Asphalt Cement

AE03

Specific Gravity at 60 ° F

P23

Asphalt Cement

AE04

Viscosity at 77 ° F

P24

Asphalt Cement

AE05

Viscosity at 140 ° F and 275 ° F

P25

Asphalt Cement

AE07

Dynamic Shear Rheometer (DSR) Test

(4)

Asphalt Cement

AE08

Superpave Direct Tension (DT) Test

(4)

Asphalt Cement

AE09

Bending-Beam Rheometer (BBR) Test

(4)

Bound/Treated Base and Subbase

TB01

Identification and Description of Treated Material and Type of Treatment

2 Test is conducted by the National Aggregates Association Joint Research Laboratory. Data are not available for all test sections.

3 Data are limited; no more data expected.

4 Certain tests developed for experiments not begun under the LTPP program (SPS-3 , -4, and -9) were not conducted according to an LTPP protocol.

13.3 IMPORTANT FIELDS

In addition to the fields described in the course of outlining the sampling and layering information tables, there are several other fields common to many tables in the Materials Testing (TST) module. While they are not critical to understanding the relational structure of the module, they do provide additional information to the analyst.

FIELD_SET
identifies materials sampled during visits to a site as related to construction events. In theory, the FIELD_SET number should be incremented for each day that materials sampling and testing were conducted. In practice, the FIELD_SET number can span a period of time during construction events. Material samples from GPS test sections are typically obtained during the first site visit after investigations to confirm the pavement structure. If a rehabilitation event is performed on a GPS test section, such as an overlay , material samples from the overlaid pavement structure will be assigned a new FIRLD_SET number. On SPS sites, assignment of a FIELD_SET number is more complicated since construction of multiple layers within a single construction event can occur. For SPS projects starting with a new or reconstructed pavement structure (i.e., SPS-1, -2, -8, and some -9's), FIELD_SET = 1 will encompass the time until the final surface layer is completed. On SPS maintenance and rehabilitation projects, FIELD_SET = 1 typically represents materials sampling and testing prior to application of the maintenance and rehabilitation treatment. On a given test section, FIELD_SET begins at 1 and is incremented for each site visit at which material samples were obtained. As such, FIELD_SET can be used as a surrogate for the actual date of sampling in identifying samples from a single section of approximately the same age.

TEST_NO
is a code field of the type TEST_NO that indicates where in the section the sample was obtained. As such, TEST_NO can be used as a surrogate for the actual longitudinal and transverse location of the sampling when identifying test results from adjacent material samples at a test section. In addition, some tests conducted on bulk samples had to be conducted on a combination of materials sampled at different ends of the section or, in some cases, at different sections at an SPS project to meet the minimum weight requirements of the test. Certain values of the code TEST_NO are used to identify such conditions. Material samples obtained at an LTPP test section are typically obtained from either just before the beginning of the section (the "approach end") or just after the end of the test section (the "leave end"). Sometimes samples are obtained from within the test section; however, this is kept to a minimum to avoid altering the performance characteristics of the section.

SAMPLE_AREA
identifies the area from which the material was sampled. During the development of the SPS materials sampling guidelines, the term "sample area" was coined to uniquely identify discrete areas at an SPS project from which material samples were obtained. Generally, the sample areas at an SPS project are numbered sequentially, starting with sample area 1 being assigned to the approach end of the first test section on the project. In addition, generally, the sample area at the approach end of a section has an odd number and the sample area at the leave end of a section has an even number. However, there is no way to verify that these generalizations hold true at any given SPS project without consulting the materials sampling plan specific to that project. This information is not available in the LTPP database at this time. The format of SAMPLE_AREA varies from table to table in the TST module (and sometimes within a table as well). Generally, SAMPLE_AREA is formatted as "##"; however, sometimes it is formatted as "SA-##", "SA##", or even "S##".

LAB_CODE
is a code field of the type LAB_CODE that identifies the laboratory that conducted the test of interest. As might be expected with a project as large as the LTPP program, many different laboratories contributed to the materials testing database. The individual laboratory that conducted any given test can be identified by the LAB_CODE field. LAB_CODE is actually a "smart code" in that the first two digits of a LAB_CODE are the same as the STATE_PROVINCE code of the State or Canadian Province in which the laboratory is located.

COMMENTS_* are codes of the type COMMENT, so this value must be linked to the codes table for a description. Most of the test results tables share a unified set of comment codes. These comment codes document expected error conditions, such as insufficient sample size or specimen fracture during testing. These tables have multiple fields for storing these codes, taking the form of COMMENTS_* (e.g., COMMENTS_1, COMMENTS_2, etc.). For cases where no appropriate comment code is available, the COMMENT_OTHER field is used to store a text comment.

13.4 UNDERSTANDING THE MATERIALS TESTING DATA STRUCTURES

Materials testing data are stored in the TST module. Additional materials characterization data are stored in the INV, RHB, MNT, and SPS# modules; however, those are based on construction history records supplied by the highway agency and are of unknown reliability.

13.4.1 Test Results Tables

Tables containing the results for specific tests can be identified based on the test designations shown in table 5. For example, data resulting from test AC03 is stored in a table named "TST_AC03". Some subgrade and unbound base layer tests that were conducted according to the same protocol, but which have different test designations, are stored in tables that have a name reflecting both test designations. For example, data resulting from test designations SS02 and UG03 are located in TST_SS02_UG03.

Some tests, such as the resilient modulus tests, generate more complex results that are stored in a related series of tables. The following sections include a general outline of each test results table in the TST module.

In each of the table descriptions below, the primary key is identified. The primary key is the list of fields required by the database to uniquely identify a single record in a particular table.

13.4.1.1 AC Test Results Tables

TST_AC01: This table contains the results of a visual examination of an AC core . It contains six fields (VISUAL_EXAM_1 through VISUAL_EXAM_6) for codes related to the observed properties of the core. These codes, of code type VISUAL_ACPC, encompass such items as stripping and degraded aggregate. An additional field (VISUAL_EXAM_OTHER) is reserved for text comments for which no numeric codes were reserved. In addition, the height of the core is stored in the CORE_AVG_THICKNESS field. The primary key consists of the STATE_CODE, SHRP_ID, FIELD_LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields. Although only STATE_CODE, SHRP_ID, FIELD_LAYER_NO, and LOC_NO are required to uniquely identify a record.

The FIELD_LAYER_NO field should not be confused with LAYER_NO as used elsewhere in the TST module. Field layering, as the name suggests, is assigned during the field visit and is often modified at the regional office after inventory and materials testing data are reviewed. To obtain the "true" layer number, this table must be linked to TST_AC01_LAYER (described below) using the STATE_CODE, SHRP_ID, FIELD_SET , and FIELD_LAYER_NO fields. (FIELD_SET is required because field layering may be assigned differently on separate field visits.)

TST_AC01_LAYER:
This table contains the information necessary to convert the field layer numbers recorded in TST_AC01 to "true" layer numbers as used in the rest of the module. In addition, this table contains the thickness of each "true" layer in so far as it can be determined from the core. This thickness is stored in the LAYER_THICKNESS field. The primary key consists of the STATE_CODE, SHRP_ID, FIELD_LAYER_NO, FIELD_SET , TEST_NO , LAYER_NO, and LOC_NO fields.

TST_AC02: This table contains bulk specific gravity test results from AC cores. Calculated bulk specific gravity is stored in the BSG field (no intermediate results are included). In addition, percent moisture absorption is available from the WATER_ABS field. Some specimens were paraffin-coated, and this is indicated by the value of the PARAFFIN_COAT field. The primary key consists of the STATE_CODE, SHRP_ID, FIELD_SET , LAYER_NO, TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AC03: This table contains theoretical maximum specific gravity test results from AC cores. Calculated maximum specific gravity is stored in the MAX_SPEC_GRAVITY field (no intermediate results are included). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AC04: This table contains extracted asphalt content test results from AC cores using trichloroethylene as a solvent. Calculated asphalt content is stored in the ASPHALT_CONTENT_MEAN field (no intermediate results are included). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AC05: This table contains moisture susceptibility test results from laboratory-compacted bulk asphalt specimens. There are only data for a limited number of sections from the SPS-1 , -5, -8, and -9 projects. A user should first check for data availability before attempting to use this data in analysis. The LTPP protocol for this test (P05) is primarily based on AASHTO T283, and the user should be familiar with the procedure before attempting to interpret the results.

In essence, test AC05 evaluates the changes in indirect tensile strength in a bituminous mixture caused by water saturation. Six specimens are molded from bulk samples using Marshall, Hveem, or gyratory compaction (the type of compaction used is stored in the METHOD_OF_COMPACTION field). Three of these cores are subjected to vacuum saturation followed by freezing and warm water soaking cycles, while the other three are kept dry. All six specimens are then loaded to failure in indirect tension. The ratio of the average strength of the dry specimens to the conditioned specimens, called the tensile strength ratio (TSR), is stored in the TENSILE_STRENGTH_RATIO field. In addition, the ratio of the coefficient of variation of the strength of the dry specimens to the coefficient of variation of the strength of the conditioned specimens is stored in the RELATIVE_VARIATION_IN_STRENGTH field.

TST_AC05 also contains several intermediate calculations for the six specimens. These calculations are stored in fields with names in the format {property name}_#_{C,U}, where the property name is the measured property (such as WIDTH or BSG), # is the name of the number, and {C,U} denotes whether the specimen is from the conditioned set or the unconditioned set.

TST_AC05 also has a slight complication regarding sample numbers. The SAMPLE_NO field denotes the sample number of the bulk asphalt concrete from which the specimens were molded and SAMPLE_NO_#_{C,U} denotes the sample number assigned to the compacted specimens. Since these specimens were tested to failure, their individual sample numbers should not appear in any other table.

The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AC_MOIST_DAMAGE:
This table contains data resulting from a visual evaluation of moisture damage to the field cores. Data exists for only a limited number of SPS-5 and -9 sections.

13.4.1.2 TST_AC07_V2_* Tables

Test results from LTPP test AC07 are stored in four related tables. These results include resilient modulus, creep compliance, and the indirect tensile strength of AC core samples. "V2" in the table names indicates that these tests were conducted according to the second version of protocol P07 used by the LTPP program. The results from the first version of protocol P07 are considered unreliable and are not available in the standard data release.

Test AC07 involves multiple tests on three specimens. The analytical procedures employ unusual data massaging, averaging, and outlier elimination methods to combine the results from these three specimens. While a full understanding of these analytical procedures is not a requirement for using the data, a basic understanding of the test procedure could prove to be useful. The test procedure is documented in LTPP Protocol P07: Test Method for Determining the Creep Compliance, Resilient Modulus, and Strength of Asphalt Materials Using the Indirect Tensile Test Device and is illustrated by figure 9. Protocol P07 is also similar to AASHTO TP9-96 with regards to the creep compliance and indirect tensile strength portions.

Figure 9. Illustration of relationships among TST_AC07* tables.

TST_AC07_V2_SPECIMEN_INFO: This table is considered the master table for a TST_AC07_V2 submodule. Key fields in TST_AC07_V2_SPECIMEN_INFO include STATE_CODE, SHRP_ID, LAYER_NO, TEST_NO , and FIELD_SET . This table also includes the sample numbers for the three specimens used (SAMPLE_NO_*), thickness information for the specimens (THICKNESS_SPECIMEN_*), diameter information (DIAMETER_SPECIMEN_*), and bulk specific gravity test results (BSG_SPECIMEN_*). This table also contains the unique filenames for the output files generated by the analysis software. These files are stored offline, but may contain data of interest to some analysts. These data are stored in the CREEP_DATA_ANAL_FILE, MR_DATA_ANAL_FILE, and IDT_DATA_ANAL_FILE_* fields, where MR stands for "resilient modulus" and IDT stands for "indirect tensile strength."

TST_AC07_V2_MR_SUM: This table contains summary data for the resilient modulus tests. These data include computed values for three load cycles and average values. The three computed values are instantaneous resilient modulus, total resilient modulus, and Poisson's ratio. The instantaneous resilient modulus is calculated using only the strain recovered during the unloading portion of the cycle, while the total resilient modulus includes the strain recovered during the 0.9-second "rest" portion of the cycle. In addition, there are fields containing a "used" Poisson's ratio. This is an output of the analysis software to account for the fact that the test procedure sometimes yields unreasonable Poisson's ratios. This table also contains the unique filenames for the three raw data files (one per specimen per test temperature) generated by the test data acquisition system and processed by the analysis software. They are stored offline. The primary key includes STATE_CODE, SHRP_ID, LAYER_NO, TEST_NO , FIELD_SET , and TEST_TEMPERATURE since this test is conducted at three different temperatures.

TST_AC07_V2_CREEP_COMP_SUM: This table contains summary data for the creep compliance tests. Creep compliance is stored in the CREEP_COMP_*_SEC fields, where * is the time interval from the initiation of the test in which the creep compliance was calculated. These time intervals are 1, 2, 5, 10, 20, 50, and 100 seconds. In addition, the value of the Poisson's ratio calculated using these data is stored in the CREEP_POISSON_CALC field. The CREEP_POISSON_USED field contains the value used in the computation as described in the preceding paragraph. In addition, the unique filenames for the three raw data files (one per specimen) are stored in the CREEP_COMP_DATA_FILE_SPECIMEN_* fields. The primary key includes STATE_CODE, SHRP_ID, LAYER_NO, TEST_NO, FIELD_SET, and TEST_TEMPERATURE since this test is conducted at three different temperatures.

TST_AC07_V2_IDT_SUM: This table contains the summary data for the indirect tensile strength test. Indirect tensile strengths for the three specimens are stored in the IDT_SPECIMEN_* fields, while the average is stored in the IDT_AVERAGE field. The calculated Poisson's ratio for this test is stored in the IDT_POISSON_CALC field, while the IDT_POISSON_USED field contains the value used in the computations as described in the discussion of TST_AC07_V2_MR_SUM. Several other fields for the initial tangent modulus, fracture energy, and failure strain exist; however, the data to populate them are not included in the standard release because the algorithms used by the analysis software are insufficiently documented, could not be reverse-engineered, and are suspect. The primary key includes STATE_CODE, SHRP_ID, LAYER_NO, TEST_NO , FIELD_SET , and TEST_TEMPERATURE, although this test is only conducted at one temperature.

13.4.1.3 Asphalt Cement Tables

TST_AE01: This table contains the results of the extraction of asphalt cement from field cores by the Abson method. The two data fields are MASS_OF_RECOVERED_BITUMEN, which contains the mass in grams of the recovered asphalt cement, and ASH_CONTENT_OF_BITUMEN, which contains the percent ash content of the recovered asphalt cement. Generally, this test is conducted to provide material for the other AE series tests, although the sample number for the input material is the same as the sample number for the output material. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AE01S is quite similar to TST_AE01; however, it was developed to accommodate data from SPS-3 projects that were tested according to different protocols. The only significant difference from the analyst's perspective is that the moisture content of the field core is also included in the MOISTURE_IN_MIXTURE field.

TST_AE02: This table contains the results of penetration tests conducted on extracted asphalt cement s at 25° C (77 degrees Fahrenheit (°F)) and 68 °C (155 °F) (although plant-sampled asphalt cements were tested for some SPS projects (see the discussion on sample numbers in section 13.4.2)). The three data fields are PENETRATION_77_F, PENETRATION_155_F, and PENETRATION_INDEX. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AE02S: This table contains data for SPS-3 projects only. Penetration was performed at only one test temperature, typically 25 °C (77 °F). The test temperature is stored in the TEST_TEMPERATURE field and the penetration is stored in the AVERAGE_PENETRATION field.

TST_AE03: This table contains the results of specific gravity tests on extracted asphalt cement. Calculated specific gravity is stored in the only data field (SPECIFIC_GRAVITY). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AE04: This table contains the viscosity of asphalt cements as measured using a cone-and-plate viscometer. This test is conducted at a nominal temperature of 25° C (77 °F). The data fields include viscosity and the corresponding shear rate for five surcharges (100, 300, 1000, 3000, and 10,000 grams), and the fracture load and failure shear stress. Calculated specific gravity is stored in the only data field (SPECIFIC_GRAVITY). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record. This test is no longer conducted.

TST_AE05: This table contains the results of kinematic viscosity testing at 135° C (275 °F) and absolute viscosity testing at 60 °C (140 °F). The summary data fields are KINEMATIC_VISC_275_F and ABSOLUTE_VISC_140_F, although some intermediate calculations are also provided. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AE06S: This table contains the absolute viscosity of extracted asphalt cement from SPS-3 projects. These data are similar to the absolute viscosity data stored in the TST_AE05 table. The test was conducted at a nominal temperature of 60 °C (140 °F). Absolute viscosity data are stored in the VACUUM_CAPILARY_VISC field and the test temperature is stored in the TEST_TEMPERATURE field. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

13.4.1.4 Tables on Aggregate in Asphalt Concrete

TST_AG01: This table contains the bulk specific gravity and percent moisture absorption of extracted coarse aggregate from AC cores. These data are stored in the BSG_OF_COARSE_AGG and ABSORPTION_OF_COARSE_AGG fields. Some intermediate calculations are also included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AG02: This table contains the bulk specific gravity and percent moisture absorption of extracted fine aggregate from AC cores. These data are stored in the BSG_OF_FINE_AGG and ABSORPTION_OF_FINE_AGG fields. Some intermediate calculations are also included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AG04: This table contains the gradation of extracted aggregate from AC cores. Gradation is determined by sieve analysis. The sieve set used consists of 37.5-mm (1½-inch), 25.0-mm (1-inch), 19.0-mm (¾-inch), 12.5-mm (½-inch), 9.5-mm (⅜-inch), 4.75-mm (No. 4), 2.00-mm (No. 10), 425-mm (No. 40), 180 mm (No. 80), and 75mm (No. 200) sieves. The percent passing each sieve is stored in a data field such as ONE_AND_HALF_PASSING for the 37.5-mm (1½-inch) sieve or NO_80_PASSING for the 180 mm (No. 80) sieve. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, TEST_NO, and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

TST_AG05: This table contains the fine aggregate shape test results for fine aggregate extracted from AC cores . Data include bulk specific gravity , percent moisture absorption, and uncompacted void content, which are stored in the BSG, ABSORPTION, and UNCOMP_VOID_AVG fields, respectively. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , TEST_NO , and LOC_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be all that is necessary to uniquely identify a record.

13.4.1.5 In Situ Tests

TST_ISD_MOIST: This table contains in situ density and moisture content measurements using a nuclear density gauge. Up to four measurements of dry density (ISD_DRY_*), wet density (ISD_WET_*), and moisture content (ISMC_*), along with their respective averages (ISD_DRY_AVG, ISD_WET_AVG, ISMC_AVG) are stored in this table. The primary key consists of the STATE_CODE, SHRP_ID, FIELD_SET, LOC_NO, and DEPTH_TOP_STRATA fields. The DEPTH_TOP_STRATA field contains the depth (in inches) from the measuring surface to the pavement surface.

13.4.1.6 PCC Test Results

TST_PC01: This table contains the compressive strength of PCC cores (although for a few SPS projects, cylinders made from fresh PCC sampled during construction were tested (see the discussion of sample numbers in section 13.4.2 for information on how to determine the sample type)). Compressive strength is stored in the COMP_STRENGTH field and the observed fracture mechanism (a code of the type FRACTURE) is stored in the COMP_FRAC_OTHER field. Several other intermediate calculations, such as the length and diameter of the specimen, are also stored. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC02: This table contains the splitting tensile strength of PCC cores and some cylinders (see discussion for TST_PC01). Tensile strength is stored in the TENSILE_STRENGTH field and the observed failure mechanism (a code of the type FRACTURE) is stored in the TENSILE_STRENGTH_FRAC field. Several intermediate calculations, such as the length and diameter of the core, are also stored. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC03: This table contains the coefficient of thermal expansion of PCC cores. The coefficient of thermal expansion is stored in the COEFF_THERMAL_EXPANSION field. In addition, a text description of the character of the aggregate type is included in the AGGR_TYPE_PCC field. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC04: This table contains the static modulus of elasticity of PCC cores. Elastic modulus is stored in the ELASTIC_MOD field, the Poisson's ratio is stored in the POISSON_RATIO field, and unit weight is stored in the UNIT_WT field. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC05: This table contains the density measurements for PCC cores. Bulk specific gravity , apparent specific gravity, density, and percent voids are stored in the BULK_SPECIFIC_GRAVITY_DRY, APPARENT_SPECIFIC_GRAVITY, DENSITY_OF_PCC, and PERCENT_VOIDS_IN_PCC fields, respectively. Several other intermediate calculations are also included in this table. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC06: This table contains the visual examination notes for PCC cores . Six fields (VISUAL_EXAM_*) are provided for visual comments of the type VISUAL_ACPC (which means that these comments must be linked to the CODES table to retrive their meaning). A seventh field (VISUAL_EXAM_OTHER) is reserved for comments for which no comment codes were provided. In addition, this table also provides the thickness of the core, which is stored in the CORE_AVG_THICKNESS field. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields , although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC07: This table contains the interface shear strength between two bonded PCC layers. This test is conducted on a core (including both layers). The maximum shear strength exhibited by the bond during testing of the core is stored in the SHEAR_BOND_STRENGTH field. Several intermediate calculations are also included in this table. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC08: This table contains the air content of hardened PCC as determined by visual examination of core specimens. Air content is stored in the AIR_CONTENT field. These data exist for only a handful of SPS-2 and -8 projects. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_PC09: This table contains the flexural strength of PCC beams that were poured from materials sampled at the time of construction. Because of the requirement for sampling during construction, data for this test are only available for SPS sections. The modulus of rupture is stored in the MODULUS_OF_RUPTURE field. Several other intermediate calculations are also included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

13.4.1.7 Test Results for Materials Specific to SPS-3 and -4

TST_CS01: This table contains data on hot-poured joint sealants for a few SPS-3 and -4 sections. There are 11 records in this table. For further information on these tests, see the SPS-3 and -4 data collection guide.

TST_CS02: This table contains data on silicone joint sealants for a few SPS-3 and -4 sections. There are only 12 records in this table. For further information, see the SPS-3 and -4 data collection guide.

TST_SC01: This table contains the results of various tests on asphalt emulsions used in surface treatments applied to SPS-3 sections only. Unlike most other tables in the TST module that contain the results for a single test, this table contains the results for many tests on the same material. Most of these tests are straightforward; however, some of them are fairly unusual (in these cases, consult the SPS-3 and -4 data collection guide). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC02: This table contains the sand equivalency of fine aggregate materials from SPS-3 sections only. The sand equivalency value, expressed as a percentage, is stored in the SAND_EQUIVALENCY field. No intermediate values are stored. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC03: This table contains the results of various tests on coarse aggregates used in surface treatments applied to SPS-3 sections only. There are three records in this table and no further data are expected. For further information, see the SPS-3 and -4 data collection guide.

TST_SC04: This table contains the flakiness index of aggregates used in surface treatments applied to SPS-3 sections only. The flakiness index is stored in the FLAKINESS_INDEX field. No intermediate calculations are stored. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC05: This table contains the results of various tests on slurry seals applied to SPS-3 sections only. This table contains a single record and no further data are expected. For further information, see the SPS-3 and -4 data collection guide.

TST_SC06: This table was intended to contain measurements of excess asphalt in bituminous mixtures obtained by using a loaded wheel and sand cohesion. Although the table structure exists, no data for this test were ever loaded into the database.

TST_SC07: This table contains the results of the wet stripping test of cured slurry seal mixes applied to SPS-3 sections only. This table contains a single record and no further data are expected. For further information, see the SPS-3 and -4 data collection guide.

TST_SC08: This table contains the results of the slurry system compatibility test for slurry seal s applied to SPS-3 sections only. This table contains a single record and no further data are expected. For further information, see the SPS-3 and -4 data collection guide.

TST_SC09: This table contains the results of tests to identify quick-set asphalt emulsions used in surface treatments applied to SPS-3 sections only. This table contains a single record and no further data are expected. For further information, see the SPS-3 and -4 data collection guide.

TST_SC10A: This table contains the gradation of aggregates used in chip seals applied to SPS-3 sections only. Gradation analysis is conducted by sieve test using the 12.5-mm (½-inch), 9.5-mm (⅜-inch), 4.75-mm (No. 4), 2.36-mm (No.8), 2.00-mm (No. 10), and 75-mm (No. 200) sieves. The percent passing each sieve is stored in fields whose name is based on the United States (U.S.) customary designation for the sieve size. For example, NO_4_PASSING contains data passing the 4.75-mm (No. 4) sieve. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC10B: This table contains the gradation of aggregates used in slurry seals applied to SPS-3 sections only. Gradation analysis is conducted by sieve test using the 8.0-mm (5/16-inch), 4.75-mm (No. 4), 2.36-mm (No. 8), 1.1.8-mm (No. 16), 600-mm (No. 30), 300-mm (No. 50), 150-mm (No. 100), and 75-mm (No.200) sieves. The percent passing each sieve is stored in fields whose name is based on the U.S. customary designation for the sieve size. For example, the field named FIVE_SIXTEENTHS_PASSING contains data for percent retained on the 8.0-mm (5/16-inch) sieve. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC11: This table contains various data used in chip seal mix designs applied to SPS-3 sections only. Factors such as the average least dimension of the aggregate (stored in AVG_LEAST_DIMENSION) and the rate of asphalt application (stored in RESIDUAL_ASPH_SPREAD_RATE) are included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC12: This table contains the asphalt content of slurry seals applied to SPS-3 sections only. The percent asphalt by weight of dry aggregate is stored in the ASPHALT_CONTENT field. No intermediate results are available. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SC13: This table was intended to contain measurements of the polish value of aggregates used in chip seal s applied to SPS-3 sections only. Although the table structure exists, no data for this test were ever loaded into the database.

13.4.1.8 Treated Base Test Results

TST_TB01: This table contains various classification results for treated base materials . The overall description of the treated material is available from the DETAIL_TREAT_MATL field. The DETAIL_TREAT_TYPE field identifies the treatment agent. Both fields contain codes of the type TREAT_TYPE. There are also two fields (PRELIM_TREAT_MATL and PRELIM_TREAT_TYPE) that may have had significance at the beginning of the LTPP program; however, they no longer provide useful information except in cases where there is no data in the corresponding DETAIL* fields, in which case they may be used as a substitute. There are various soil geology-related fields and aggregate-type fields that may or may not be populated based on the nature of the treated material. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, and TEST_NO fields , although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_TB02: This table contains unconfined compressive strength results for treated base materials. Compressive strength (in pounds force per square inch (lbf/inch2)) is stored in the COMP_STRENGTH field. Fracture mode (a code of the type FRACTURE) is stored in the COMP_STRENGTH_FRAC field. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

13.4.1.9 Unbound Materials Testing Results

TST_SS01_UG01_UG02: This table contains the gradation of unbound coarse-grained granular base, subbase, and subgrade materials. Gradation analysis is conducted by the washed sieve test, with the washed fines included with the percent passing the 75-mm (No. 200) seive. The sieve set specified in the test protocol consists of the 75-mm (3-inch), 50-mm (2-inch), 37.5-mm (1½-inch), 25.0-mm (1-inch), 19.0-mm (¾-inch), 12.5-mm (½-inch), 9.5-mm (⅜-inch), 4.75-mm (No. 4), 2.00-mm (No. 10), 425-mm (No. 40), 180-mm (No. 80), and 75-mm (No. 200) sieves. The name of field is based on the U.S. customary sieve size name. For example, ONE_AND_HALF_PASSING contains data for amount of material passing the 37.5-mm (1½-inch) sieve. In addition, the total dry weight of the sample before washing is stored in the SAMPLE_WT field and the moisture content of the sample prior to testing is stored in the MOISTURE_CONTENT field. If data are unavailable for a given material, check TST_SS02_UG03. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SS02_UG03: This table contains the gradation of unbound fine-grained granular base, subbase, and subgrade materials. Gradation analysis is conducted by sieve test combined with hydrometer analysis. The sieve set used is identical to that used in TST_SS01_UG01_UG02, as are the associated field names. In addition, the hydrometer results are expressed as percent size smaller (passing) 0.02 mm (780 microinch), 0.002 mm (78 microinch), and 0.001 mm (39 microinch). These data are stored in fields whose name is based on the SI measurement convention. For example HYDRO_02 contains data passing, or smaller than, 0.02 mm (780 microinch). These values are also expressed as percent gravel (GT_2MM), coarse sand, fine sand, silt, clay, and colloids in fields of the same name. If data are unavailable for a given material, check the TST_SS01_UG01_UG02 table. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SS04_UG08: This table contains the general classification of unbound granular base, subbase, and subgrade materials . Information in this table includes maximum particle size (MAX_PART_SIZE); soil color (SOIL_COLOR); 10 fields for the description codes of the type SOIL_CRITERA, including American Society for Testing and Materials (ASTM) classification (DESC_CODE_*); and AASHTO classification (AASHTO_SOIL_CLASS). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SS06: This table contains the modulus of the subgrade reaction (k-value) of unbound subgrade layers. This subgrade reaction is measured by static plate loading. Raw modulus (in lbf/inch2/inch) is stored in SOIL_MOD_UNCORRECTED, while the modulus as corrected for plate bending is stored in SOIL_MOD_CORRECTED. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, and LOC_NO fields.

TST_SS08: This table contains subgrade in situ moisture and density measurements . These measurements are taken on thin-wall tube or split-spoon specimens. Moisture content is stored in the MOISTURE_CONTENT field and dry density is stored in the DRY_DENSITY field. A few intermediate calculations are also available. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

Test specimens are obtained by thin-wall tube sampling. Unconfined compressive strength is stored in the UNCONFINED_COMPRESSED_STRENGTH field. In addition, the moisture content and dry density of the specimen are stored in the MOISTURE_CONTENT and DRY_DENSITY fields, respectively. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SS11: This table contains hydraulic conductivity measurements on subgrade materials obtained using a flexible-wall permeameter. Data are only available for a limited number of SPS-1 , -2, -8, and -9 sections. Test specimens are either thin-wall tube samples or laboratory remolds. Hydraulic conductivity is stored in the AVG_HYDRAULIC_CONDUCTIVITY field. Several intermediate calculations are also available. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_SS12: This table contains potential vertical rise (PVR) values for subgrade materials . These data are intended for use in identifying expansive soils. This total is the summation of the PVR for the first 6.1 m (20 ft) of subgrade depth, tested at 0.61-m (2-ft) intervals. Only three records are available in the database.

TST_UG04_SS03: This table contains the Atterberg limit test results for unbound granular base, subbase, and subgrade materials. The liquid limit, plastic limit, and plasticity index are stored in the LIQUID_LIMIT, PLASTIC_LIMIT, and PLASTICITY_INDEX fields, respectively. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_UG05_SS05: This table contains standard Proctor test results for unbound granular base , subbase, and subgrade materials. Only the optimum dry density and moisture content are stored in the table (in the MAX_LAB_DRY_DENSITY and MAX_LAB_MOISTURE fields, respectively). The other points on the moisture-density curve are not loaded into the database. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_UG09: This table contains the permeability of unbound base and subbase material s as tested under constant head using a rigid-wall permeameter. Measured hydraulic conductivity is stored in the AVG_HYDRAULIC_CONDUCTIVITY field. Some intermediate calculations are also included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, and TEST_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_UG10_SS09: This table contains the in situ moisture content of unbound base, subbase, and subgrade materials as measured by drying samples in the laboratory. Measured moisture content is stored in the MOIST_CONTENT field. No intermediate calculations are stored. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

13.4.1.10 TST_UG07_SS07_*

The TST_UG07_SS07 family of tables contains resilient modulus data for unbound granular base, subbase, and subgrade materials. Testing is conducted according to LTPP Protocol P46. Analysts are encouraged to review the test protocol before using the data. The relational structure and some test details related to this submodule are illustrated in figure 10.

TST_UG07_SS07_A: As shown in figure 10, this table contains basic information on the tested specimen. The information on specimens molded in the laboratory from bulk material includes initial length (INITIAL_LENGTH), initial area (INITIAL_AREA), moisture content after testing (AFTER_MOIST_CONT), dry density (DRY_DENSITY), and the strength of the specimen as measured in the quick shear test (STRENGTH). This table also contains additional information used in determining the moisture-density target, including the in situ moisture and density (IN_SITU_MOIST and IN_SITU_DENSITY, respectively), and the maximum Proctor density and the associated optimum moisture content (MAX_DRY_DENSITY and OPT_MOIST_CONT, respectively). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET, LOC_NO, TEST_NO, and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO can be used to uniquely identify a specimen.

TST_UG07_SS07_B: As shown in figure 10, this table also contains basic information on the specimen being tested. The table contains similar information to the TST_UG07_SS07_A table; however, it is for undisturbed thin-wall tube specimens only. As in the previous table, the information stored includes the initial length (INITIAL_LENGTH), initial area (INITIAL_AREA), moisture content after testing (AFTER_MOIST_CONT), dry density (COMP_DRY_DENSITY), and the strength of the specimen as measured in the quick shear test (STRENGTH). The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , and SAMPLE_NO fields, although STATE_CODE, SHRP_ID, and SAMPLE_NO should be sufficient to uniquely identify a specimen.

TST_UG07_SS07_WKSHT_CYCLES: This table contains the resilient modulus, loading conditions, and intermediate calculations for each load sequence. Data for both remolded and thin-wall tube specimens are stored in this table. The loading condition stress states are a combination of the confining pressure (stored in the CON_PRESSURE field) and the nominal maximum applied axial stress (stored in the MON_MAX_AXIAL_STRESS field). The test protocol typically requires 3 levels of confining pressure and 5 levels of nominal maximum applied axial stress for a total of 15 unique stress states. (For type 1 materials, only 13 stress states are used; the highest two axial stress states for the highest confining pressure are not used.) For each stress state, 5 loading sequences of 100 cycles are applied to the specimen. Thus, 75 records are created in this table for the typical 15 stress states. Applied cyclic stress is stored in APPLIED_CYCLIC_STRESS, corrected resilient deformation is stored in CORR_VERT_DEF, resilient strain is stored in RES_STRAIN, and resilient modulus is stored in RES_MOD. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO , SAMPLE_NO, CON_PRESSURE, NOM_MAX_AXIAL_STRESS, and CYCLE_NO fields, although STATE_CODE, SHRP_ID, SAMPLE_NO, CON_PRESSURE, NOM_MAX_AXIAL_STRESS, and CYCLE_NO should be sufficient to uniquely identify a specimen.

TST_UG07_SS07_WKSHT_SUM: This table contains the average resilient modulus and some intermediate calculations for the five loading sequences at each stress state. Data for both remolded and thin-wall tube specimens are stored in this table. The stress state is indicated by the combination of the CON_PRESSURE and NOM_MAX_AXIAL_STRESS fields. Average cyclic stress and resilient strain are stored in the APPLIED_CYCLIC_STRESS_AVG and RES_STRAIN_AVG fields, respectively, with standard deviations stored in APPLIED_CYCLIC_STRESS_STD and RES_STRAIN_STD. The average and standard deviations of the resilient moduli values calculated for that specimen and the stress state are stored in the RES_MOD_AVG and RES_MOD_STD fields, respectively. Several intermediate calculations (including maximum axial stress, contact stress, and average deformations) are also included. The primary key consists of the STATE_CODE, SHRP_ID, LAYER_NO, FIELD_SET , LOC_NO, TEST_NO,

SAMPLE_NO, CON_PRESSURE, and NOM_MAX_AXIAL_STRESS fields, although STATE_CODE, SHRP_ID, SAMPLE_NO, CON_PRESSURE, and NOM_MAX_AXIAL_STRESS should be sufficient to uniquely identify a specimen. Tthe location of the hole; the dimensions of the hole; and, in some cases, other information such as depth to refusal.

13.4.2 Sampling Information Tables

Most of the test results tables contain very little sampling information. Field samplin information is stored in the TST_HOLE_LOG and TST_SAMPLE_LOG tables.

TST_HOLE_LOG: This table contains a record of each core hole, bore hole, or text pit cut in an LTPP section for the purpose of extracting material samples. This record includes the date the hole was dug; the location of the hole; the dimensions of the hole; and, in some cases, other information such as depth to refusal.

LTPP Database Tip!

For all samples extracted from an in-service pavement, the date of sampling is located in the TST_HOLE_LOG table. The date the sample was tested, where available, is located in the same table as the test results.

The data in the TST_HOLE_LOG table can be linked to data in the various test results tables by use of the STATE_CODE, SHRP_ID, and LOC_NO fields. The STATE_CODE and SHRP_ID fields together uniquely identify a test section, as described elsewhere in this document. Within a given test section, the LOC_NO field uniquely identifies a hole.

In addition to being useful for linking to TST_HOLE_LOG, the value of LOC_NO contains additional information about the hole. The format is as follows:

### Location number: Up to a three-digit location number is assigned sequentially to each location type on each test section. An asterisk (*) is used to identify cases where samples from the same layer were combined to satisfy minimum testing requirements.

For core sample locations taken at specified time intervals from the start of construction on SPS?9 projects, a letter is appended to the end of the SAMPLE_NO. It is not used for other sample locations. The letter is used to designate the approximate time from paving to coring as follows:

TST_SAMPLE_LOG: While TST_HOLE_LOG contains data for each test hole cut into an LTPP section, often multiple samples are extracted from a given test hole. Additional sampling information can be found in TST_SAMPLE_LOG. This information includes the depth from which the sample was taken and a description of the material sampled.

Records in TST_SAMPLE_LOG can be linked to records in the various test results tables using the STATE_CODE, SHRP_ID, and SAMPLE_NO fields. While STATE_CODE and SHRP_ID uniquely identify a test section, SAMPLE_NO uniquely identifies samples retrieved within that test section.

As with LOC_NO, SAMPLE_NO contains useful information and permits linking between various TST tables. SAMPLE_NO is typically a four- to six-character value with the following format:

Sample number: Up to a three-digit sample number assigned sequentially to each sample with the same sample and material type designation. An asterisk (*) is used to identify cases where samples from the same layer were combined to satisfy minimum testing requirements.

For core sample locations taken at specified time intervals from the start of construction on SPS?9 projects, a letter is appended to the end of the SAMPLE_NO. It is not used for other sample locations. The letter is used to designate the approximate time from paving to coring as follows:

13.4.2.1 Other Sampling Information Tables

The TST_HOLE_LOG and TST_SAMPLE_LOG tables contain information for all samples of in-place materials. This includes virtually all sampling conducted on GPS test sections. However, many SPS sections and GPS overlay sections also include bulk samples of materials obtained during construction prior to placement on the roadway. Sampling information for these materials is located in one of a series of additional tables (based on material type).

TST_ASPHALT_CEMENT: This table contains sampling information for bulk samples of asphalt cement obtained from the plant. Each asphalt sample has a LOC_NO and a SAMPLE_NO that are unique to the section. The table also includes additional information about the plant itself.

TST_FRESH_PCC: This table contains information about test cylinders and beams cast on site from concrete used in construction. Each batch of concrete sampled has a unique LOC_NO. Up to six cylinders and three beams were cast from each batch of sampled material. Each cylinder and beam has a unique SAMPLE_NO. In addition, this table contains information about the slump and air content of the sampled concrete.

TST_SAMPLE_LOG_LAB: This table contains information about specimens molded in the laboratory from bulk AC samples . This table is unusual in that it has an "input" sample identification (SAMPLE_NO) that identifies the bulk material used and an "output" sample number (SAMPLE_NO_LAB) that identifies the compacted specimen that will be used in further testing.

TST_SAMPLE_LOG_SPS_3_4: This table contains sampling information for chip seal , slurry seal, or joint sealant material obtained in the field for SPS-3 and -4 sections only. Treatment of LOC_NO and SAMPLE_NO are similar to TST_SAMPLE_LOG.

TST_UNCOMP_BITUMINOUS: This table contains sampling information for uncompacted AC specimens obtained during construction. LOC_NO and SAMPLE_NO are unique for a given test section. In addition to the time and location the sample was taken, this table also contains information on the plant where the asphalt concrete was mixed.

13.4.3 Layer Tables

The TST module is the primary source for layer information in the LTPP database . There are two tables containing layer thickness information: TST_L05A and TST_L05B. In general, TST_L05A can be thought of as the source for measured layer thickness data and TST_L05B can be thought of as the source for representative layer thickness. This representative layer thickness is based on data stored in TST_L05A in addition to the deflection testing results, inventory data, and engineering judgment. LTPP test sections are selected, in part, based on their expected homogeneity. As with any real-world pavement structure, variations in material type and thickness exist within a test section. Within-section thickness measurements on some layers exist for some SPS test sections where rod-and-level measurements were taken during the construction event or by ground-penetrating radar.

LTPP Database Tip!

Select the appropriate layer thickness data source based on analytical needs. For most analyses, data in TST_L05B is sufficient.

TST_L05A: This table contains multiple-layer thickness information. Each record in TST_L05A is uniquely identified by the STATE_CODE and SHRP_ID of the section, the CONSTRUCTION_NO that identifies the period of time for which the structural information is valid (for more information on CONSTRUCTION_NO, see the description in section 3.1), and the LAYER_NO that identifies the discrete material layers in the pavement section. Each record also includes a DESCRIPTION, which identifies the function of the layer in the pavement system, and a LAYER_TYPE indicating the general composition of the layer.

For each record in TST_L05A, there are three sets of fields containing measured thickness, the method by which the thickness was determined, and a detailed description of the material comprising the layer. These sets correspond to measurements taken at the approach end of the section (LAYER_THICK_STATION0, MATERIAL_CODE_STATION0, and MEASURE_TYPE_*_STATION0), within the section (LAYER_THICK_WITHIN, MATERIAL_CODE_WITHIN, and MEASURE_TYPE_*_WITHIN), and the leave end of the section (LAYER_THICK_STATION5, MATERIAL_CODE_STATION5, and MEASURE_TYPE_*_STATION5).

For an LTPP section, a LAYER_NO of "1" is always assigned to the lowest identifiable layer in the pavement section, with progressively higher LAYER_NO's assigned to the higher layers. Although this may seem counterintuitive, it allows the same layer numbering scheme to be maintained as new layers are added to the surface of a section because of maintenance or rehabilitation treatments. For example, if a section has an uppermost layer with a LAYER_NO = 5 and that section receives an overlay , the new surface layer will now have a LAYER_NO = 6; however, the lower layers will still be referenced to the same LAYER_NO's.

Sometimes a layer will be entirely removed by milling; however , it will still be referenced by the same LAYER_NO, but the thickness will now be 0. Again, while this may be counterintuitive, it maintains the referential integrity of the TST module. For the example above, if the surface layer is milled and replaced, LAYER_NO = 5 will have a thickness of 0 and a new LAYER_NO = 6 will be added to the database for the next CONSTRUCTION_NO. Therefore, materials tests keyed to a specific LAYER_NO will represent the same layer in the pavement structure regardless of the CONSTRUCTION_NO.

TST_L05B: This table contains representative thickness information based on multiple data sources and engineering judgment, as opposed to the measured layer thickness data stored in TST_L05A. Since TST_L05B is of critical importance to the database as a whole, it is more fully described in section 13.4.4.

Like TST_L05A, each record in TST_L05B is uniquely identified by STATE_CODE, SHRP_ID, CONSTRUCTION_NO, and LAYER_NO. The representative thickness of the layer is stored in the REPR_THICKNESS field and the overall material type is stored in the MATL_CODE field. In addition, there are three fields that contain comment codes on how the representative thickness was arrived at (LAYER_COMMENT_*) and an additional field for text comments (COMMENT_NOTE).

TST_L05B has an additional field (PROJECT_LAYER_NO) that is useful for linking data elements between sections at an SPS project. Its use is further described in section 13.3.4.

13.4.3.1 Other Layer Tables

LTPP Database Tip!

Some basic materials characterization information is available in the INV module, SPS*, and the RHB and MNT modules as appropriate to the section type. Since this information is not collected under the auspices of the LTPP program, its reliability is unknown. However, it may be of value in cases where such data are not available in the TST module.

Relating materials testing data back to the layers that they represent is fairly straightforward for GPS sections. Generally, all that is needed is the STATE_CODE and SHRP_ID of the section, and the LAYER_NO of the layer within that section. Relating such data for SPS sections, however, can be more complicated.

An understanding of some of the fundamental differences between the SPS and GPS sections is necessary for understanding why SPS materials testing data are more complicated to access. GPS test sections are stand-alone in that each section was sampled as a discrete entity. SPS sections, however, are clustered with several adjacent sections comprising a project. One of the advantages of such clustering is that these sections can share data (e.g., traffic, climate, and materials testing data). However, this clustering comes at the price of a slightly more complicated data structure.

To illustrate these complexities, consider a hypothetical SPS project with two sections (1 and 2). Figure 11 shows a plan view of this project. Figure 12 shows the cross-sectional view of this hypothetical project and the layer numbering.

As described in section 13.4.3, the layering of an LTPP section can be obtained from the TST_L05B table. From figure 12, we can see that the structures of the two sections are similar, except that section 01 has a granular base, while section 02 has a treated base. In both cases, four layers have been identified. Thus, in both cases, they have been numbered 1 through 4 (despite the fact that layer 2 is different in composition for each section).

In addition to the section layer numbers (these are sections at an SPS project), TST_L05B also contains project layer numbers for these sections. Project layer numbers identify layers consisting of materials from the same source placed at the same time with the same methods. Since the project layer numbers for the surface asphalt layer and the subgrade at these two sections are identical, we now know that these layers are continuous and we expect that they should have very similar properties.

LTPP Database Tip!

When seeking materials test results for an SPS section, project layer numbers can be used to find tests of the same material on a different test section. Although the material source and placement methods may be identical, construction variability may result in differences in material properties.

Now that we know that layer F for these two sections is virtually identical (barring construction variability stemming from the fact that they are 366 m (1200 ft) apart), we can cross-reference materials testing data between these sections. For example, if an analyst wishes to calculate the air void content of layer 4 on section 02, the analyst would first have to find the bulk specific gravity and theoretical maximum specific gravity of that material in the LTPP database. However, if only bulk specific gravity results are available for that layer, the analyst could use a theoretical maximum specific gravity result for layer 4 at section 01, since there is good reason to expect that the material properties are similar.

13.5 KEY TABLES

13.5.1 TST_L05B

The TST_L05B table can be considered the master table for the entire TST module. It is the best source for pavement layer thickness information. The layer thickness values stored in this table are those that the regional data collection contractors recommend as being the best representative values based on the inspection of field sampling information, deflection measurements, and laboratory measurements on cores. Therefore, each of the data elements included in this table is discussed below.

SHRP_ID is a four-character identifier for the test section. It must be combined with STATE_CODE to be unique for a test section.

STATE_CODE uses the STATE_PROVINCE code in the CODES table to define the owning agency and geographical location of the test section. Note that STATE_PROVINCE codes exist for many nations that are not currently participants in the LTPP program.

CONSTRUCTION_NO identifies changes in the pavement structure caused by rehabilitation treatments or application of maintenance treatments. When a section first enters the LTPP program, it is assigned a CONSTRUCTION_NO of 1. The CONSTRUCTION_NO is incremented by 1 for each subsequent maintenance or rehabilitation event regardless of its impact on the pavement structure. For example, crack sealing could cause a new construction event to be generated even though it does not cause a change in the experiment assignment or pavement structure. This table and EXPERIMENT_SECTION are the only tables in which CONSTRUCTION_NO is manually entered. In all other tables in the database, CONSTRUCTION_NO is computed based on the date of the event.

LAYER_NO is a unique identifier for the layers in the pavement system. A LAYER_NO of 1 is always assigned to the lowest layer in the pavement system, with each identifiable layer above it getting a progressively larger LAYER_NO.

PROJECT_LAYER_NO is an SPS project-level layer identifier. Use of this field can allow layers in different sections on the same SPS project with the same material properties to be identified.

DESCRIPTION is a code of the type DESCRIPTION that describes the function of the layer in the pavement structure. Common DESCRIPTION codes are 03 for the original pavement surface, 01 for an overlay , and 07 for a subgrade.

LAYER_TYPE is a code of the type LAYER_TYPE that provides a basic description of the composition of the layer. Common LAYER_TYPES are "SS" for subgrade, "GS" for granular subbase, "GB" for granular base, "AC" for asphaltic concrete, and "PC" for portland cement concrete.

REPR_THICKNESS is the representative thickness of the pavement layer. It is a best estimate of a single representative value of layer thickness based on several data sources, including cores, analysis of deflection data, and elevation surveys.

MATL_CODE is a code of the type MATERIAL that describes the material composition of the layer. It is much more specific than the general LAYER_TYPE classification.

LAYER_COMMENT_1 (_2, _3) are comments of the type L05B_COMMENT_CODES that describe how the representative layer thickness was determined.

COMMENT_NOTE contains additional comments (if any) about the layer.

INV_LAYER_NO is a link to the agency-supplied layer information in the INV module. This is necessary because the agency-provided data and site-specific measurements taken by the LTPP program do not always agree on the detailed layering structure at the test section location. For example, the presence of embankments at the test section site is often not included in the agency data.

INV_LAYER_NO_2 is used in circumstances where a single layer as described in TST_L05B is described as two separate layers in the INV module.